Wind, buoyancy changes and mixing contribute to ocean transport.
Key knowledge
Ocean circulation includes wind-driven currents and overturning associated with buoyancy changes from heating, cooling and freshwater exchange. These processes redistribute heat and materials. Deep-water formation and the return of water toward the surface involve connected dynamics rather than a single uniform conveyor speed.
Conditions and scope
Temperature, salinity, winds, mixing and geometry interact; density changes alone do not describe every current.
A global-conveyor picture is a simplification, not a fixed future forecast or one circuit followed by every water parcel.
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Ocean circulation includes wind-driven currents and overturning associated with buoyancy changes from heating, cooling and freshwater exchange. These processes redistribute heat and materials. Deep-water formation and the return of water toward the surface involve connected dynamics rather than a single uniform conveyor speed.
Ocean circulation redistributes heat and interacts with surface heat exchange.
For sufficiently slowly varying large-scale flow away from strong friction, horizontal pressure-gradient and Coriolis accelerations can approximately balance. With nonzero f, the geostrophic velocity follows isobars on a constant-height surface. Small Rossby number supports the approximation but does not remove boundary or transient effects.
The balance also applies to suitably slow interior ocean currents.
Seawater density depends on temperature, salinity and pressure. A stable density structure resists vertical displacement, while cooling or salinity changes can promote sinking under appropriate conditions. Winds, buoyancy fluxes and mixing connect surface exchange to interior circulation, rather than one conveyor analogy determining every flow path.
Density and mixing supply constraints beyond a broad circulation label.
In the steady idealized surface Ekman layer, vertically integrated mass transport is ME=τ×ẑ/f. Its direction is perpendicular to applied wind stress, reversing with the sign of f. Transport divergence/convergence can induce vertical exchange with the interior through continuity.